Character identification system employing plural resistor-correlation masks



Jan- 26, 1965 J. s. BRYAN ETAL CHARACTER IDENTIFICATION SYSTEM EMPLOYINGPLURAL REsIsToR-coRRELATIoN MAsKs 4 Sheets-Sheet l Filed Jan. 15, 1962@UAA/7725.0 l//DEO 007' CHA/Wij F. TEACHER ffm/SJW Jan. 26, 1965 J. s.BRYAN ETAL 3,167,745

CHARACTER IDENTIFICATION SYSTEM EMPLOYING PLURAL. REsIsToR-CORRELATIQNMAsKs Filed Jan. 15, 1962 4 Sheets-Sheet 2 J. s. BRYAN ETAL `3,167,745CHARACTER IDENTIFICATION SYSTEM EMFLOYING l Jan. 26, 1965 PLURAT..RESISTOR-CORREJLATION MASKS 4 Sheets-Sheet 3 Filed Jan. l5, 1962 un l.@.WNIN mm TN.QQQQQQQQN-Q mmm Q.QTQQQQQQQQQ MMM. N-N.Q\N\N-TN\N|T 1&5Q|Q-Q\QQQQ\Q.Q\Q- .am N. Q Q Q\Q\ Q\ Q :QN Q QQI mw.. N.NQ\Q NQQQQQQQQQQ- TQQQWNQQQQQQQQ. QQQYQvTQQQQTQ QMN N- Q QQ Q QIN- Q NQ Q T TQNQQN-NN NI Q N NIT N QQNT T TQ QN NNQN Nl. QT N Q QN N- Q. Q Q\ QT@ Nl QN- Q N k NN. T N T Q NN .2f Q T N. Q QN Q TQ- QlQ- Q N NN QS, NL Q- N-QQ NQ N TNQ- Q Q QQ Q NN QQQQENQINQQNQQ QQQ N- Q Q QQQNYQ Nl? QQ NN Q QQ Q|Q`NQQNQNQ`QQQNN|Q| QQ Q N- N QT. Q NNN QQQTNINUT NQ Q .TQQQNQNQQNQINNN N-\.Q.QQ.Q-QQQTTN- QN\ N TTQQQQQQQQNQ QNN` `\.`\.QQQQQQQ\-Q WRR Jan.26, 1965 J s, B-RYAN ETAL 3,167,745

CHARACTER IDNTIFICATION SYSTEM-EMPLOYING PLURAL. RESISTOR-CORRELATIONMASKS Filed' Jan. 15, 1962 4 Sheets-Sheet 4 f7 E C' JJTEPJ /7/ /73 /95za/ /70 /yz /74 /y /27 /fa /79 20a 202 2o 3u '35" so @o Fvg. 7.

202 6 lu L t /JL A A A A A l/V V W p4 INVENToR assists ce Patentes.iai-i. as, tess CHARACTER .IDENTIFICATION SYSTEM EMBLY- ING PLURALRESISTOR-CORRELATIN MASKS James S. Bryan', Hatboro, and Charles F.Teacher, Philadelplxia, Pa.,v assignors 'to Philco Corporation,Philadelphia, Pa., a Acorporation of Delaware Filed Ian. i5, 1962, Ser.No. 166,082 7 Claims. (Ci. 34h-146.3) v

The present invention relates to character recognition systems and moreparticularly to resistor-correlation mask recognition devices employedin such systems.

' Systems are known, for scanningcharacters to obtain a signalhavinganamplitude versus time variation which is characteristic ofthe'shape ofthe scanned'character. Forexample, the'charactermay be recordedin magnetic ink on a no nmagnetic. background and/or the charactermaygbe recorded in acolor ,or shade thatV contrasts with thebackground.The "area containing the character is scanned optically or with anappropriate magneticsensing means tok generate the signal characteristicof the character. Since the'novelty ofv the' present invention does notreside inthe vcharacter scanning means. per seitwill be assumed =inthefoi1owing description that the characters are recorded in black onaA"White background. However 'it is to'be understoodl that the inventionis ynot to be` limited to this vform` of characterrecordingior'to thespeciticscanning system which is shownibywayfof illus@y tration.

In the presently preferre'diforms Aof pattern recognition systems, towhich the present invention relates, thesignal derived vf romscanningthecharacte'r is converted to a series of pulses whichhav one valveifl'the area scanned during a given timek 7Vincr/ement includes v anyportion of the character, lile'. any blacka re a,'and aldilferent valueif the area scanneddoes notfcontain any portion offthe character.v Meanssuch' asastepping shiftl register and a tappedtdelay line'igare'employed -to supply selected 'ones of these pulsesfin vdifferent'-ot)mbination s` tofthe several units of a pluralityiof` weighted resistor'addernetworks which are known in *the character recognition art vresistorfcorrelationmasks.: In prior artsys'tems one such maskV isprovided for each character to berecognized Irr" the'systems of theprior art the polarity of thesignal supi pliedto the mask and the Valvesof the resistors making uprthe masks'iare so vselectedtlie the output ofthefaddery network 'ormask has a maximum ofone polarity :when

ltmaskf t ,.1 .-1

."One of the major disadvantages of masks of this type is'that it aheavy weightiis given to any part of the mask the area' scanned'includes .the character associated with i to distinguish between `two,`similar characters, for exam? t ple, if in the mask for R' the portionof the slant leg isl given relatively heavy weightso as to dist inguishbetween RIandP, the weighting'fof the'jremainder of the mask generalthesey and other objects of the invention,` are achieved'by providing aplurality of masks for at leastsome ofthe characters to be recognizedand fruther providing means for combining the output of the severalmasks associatedwith a given character so that an output orrecognitionsignalis produced only in response to the simultaneous generation of arecognition signal by all masks associated witha Vgiven'character;A Fora better` understanding of the present invention together with other yand further objects thereof, reference should now be made to thefollowing detailed description which is to 'be read inconjunction withthe accompanying drawings in which FIG.` l is a block diagram of Vat'ypicalcharacter recognitions'ystem employing' resistor-correlationmasks;

FlG. 2 `is a more detailed block diagram of the pulse Shaper shownin'FIG. 1; i l

FIG. 3 is a Vcircuitdiagram of a portion of the shift register AshowninFIG. 1; f

FIG.v 4 is a circuitdiagram partially `in.block of the multistep masksystem whichconprises the present invention g" FIGS; 5 A- 5C aretables'showingtypical `values, and `ypical connections for amulti-levelresistoncorrelation mask;`

` FIG. v6 is ya pictorial view'showing vatypical scanning ras'terfor thesystem of FIG. l; 'i

FIG. 7 is a plot showing the signal generated by the scanningVportion-of the system of FIG. 1 for a particular are illustrativek ofthe operation of the system 'of FIG. 1; and:

l FIG. 9 is a plot showing a Ltypical waveform kgener'atekdby one ofthecorrelation masksof FIG. 4.511 v #Inthesystem shown'in FIG.` 1, vthecharactersy tojbe' recognizedare .assumedto be non-reflectiveVcharacters 20 appearingon'a white orfreective'sheet 22. Sheet/'22 maybe' aletter, envelop5book page, etc. 'Cathode'ray tube 24 forms ltheoutputfofa'ilying'spot vscanner system which alsoincludesverticaliposition control-26, horizontal position'control28,`vertical scan generator 30, horif" -zontall scany generator 32, scansynchronizing meansf34,..

vertical'sizccontrol 36 and horizontal size control 3:3.

The loutputs of vertical -scan generator 301 and horizontall scangenerator SZare supplied to'thedetlectionyoke itl of cathode ray tubel24. A lens 42 is provided forfocu'singthe spot generatedfny cathode raytube' 24A onto'shee't 22, that is, lens 42 irnag'es'the` screen of tube-24 onto becomesless significant; -As alresult the mask may be incapableofdistinguishing betweenLother pairs .of characy tersjsuch lasjR and Kor P `and F. lf heavy weight is .Hr given 'to that part it maybeimpossible tudiaerenaa between Rand P. n f f It is an object of thepresent invention to provide 'an'.

.improved resistor-correlation masksystem which is cap# able of moreprecisecharacter differentiationthan systems vof the prior art. Y

'It is' afurther objectvto provide a 'resistor-correlation mask systemwhich does not require disproportionate weighting'vof any portion of thern ask.

A further object ofthe presentinvention'is to provide'v an improvedresistor maskt'system -inwhich'a plurality of distinctive areas ofafcharacter maybe given'equal andicontrolling weight. v

Vsheet v2?.. As vwill be" explained in more detail-V presently,

the ying spotV scanning system just described` scans an varea of sheet22' with a" rectangular raster, the size ofthe `fraster 'on'sh'eet 22being"Slightlylarger than one of the characters.- The `areascanned bythe raster may be selected` by adjusting vertical position control 26and hori- 5 Zontal position control 28 to'causethe raster to vcoincidewith any selected characterV on sheet 22.- The scanning' of ltherasteriscontrolled by vpulses supplied at 4input 44 to synchronizingcircuitlefv j The area of thefsheetlaZZ illuminated by the raster"supplied by tube 24Vis imaged'onto the'photosensitive surface4ofphoto-multiplier tube 46-by means of a lens Y lav 4Lens dmayvimagetheV entire-sheet 2.2y onto lthe photosensitive 'surfaceofphotomultiplier tube '46. However, only the area illuminated by theraster is effective in producing a signal at the outputl ofphot'ornultiplierv v tube 46.

The output of photomultiplier 46 `supplied tol alp'ulse" shaperSZ whichreceives a secondinput from a clock' pulse source represented -bytheiarrow, 54. Y Pulse Shaper .SZrnay be any circuit which willconvertthetime varying signal suppliedby 'p hotornultiplierd'to a pnlsesig After fifty shift pulses have been appliedfto register S641` lgrand4197 is stored in the 13th land 15th stages respec-,

tively. Similarly the information-represented ofqpulses. 1978 and 199 isstored in the third and fifth stages, respec# t tively.

`At 'the' end offss' shift paises blac inrormatonwin the informationformerly contained inthethird' throughY Y the/eighth stages is nowcontained in *fthe 23rd through the 28thl stages and the informationrepresentedbyipulses. p

an foutput signal which exceeds threshold,levelrltA inv which exceedsthethreshold level 'in-'the'v vicinity ofthe thshiftpulse'if the.remaining characters of theggroup. j are. scfanned.' YIn latriple mask,.or1e;orv kmore fof lthe, t

' characters recognized by the first mask may Vbe recognized IV also bythersecondv mask. Also. the` secondA mask may recognize, ..i.e.V providean Qutputsignalabovefthe pre-v be stored in the 1stf3rd5 ll l'th, 13th,21st, 23rd, 31st-36th t the first mask and one` or more ofathe`characters recogsta'ges ofshift register JSti,Y In .the matrix `'arrayof FIG, URE 8 `thestages storing thel black information repro-f Y ducesin block form the P of FIGURE'-6. InresponseY to the 159th shiftpulseuthe information contained in each of thestages just` mentionedwill again advance tothe vnextfffhighe'r lnumberedstagep `In the matrixarray of stages shown in FIGURES thisv will. havedieeifect `of movingthe blockletter P down one space'as shown in FIGURE 8D. FGS@ SEfand SF;represent the position Vof the-information in the shiftregister 56after. the 64th 'following-letters w,.ej,y r, La: b,.a', x,l ckv and nbut will v' 'notu produce a signalexoeedingthe. threshold level ,fory

shift `pulses and the 80thV shift pulses, respectively. It

Willi-bve seen-from,FIGUREr SFthat after thev 80th shift` rpulsetheinformation is centered-in lthe A,shift register 56.` 1" As shown inVFIG.` 8G, at the end of: l02zshift pulses; i vpulseVvltlfwhich'represents the lowest portion `of the? .uprightstroke of theletter YPqoccupies the ,last srtageyof shift registerA 56V, lBetweenthe: 58th shift pulse and the' l02nd` shift pulse the letterl P willhave assumed every possible-position within shift' register 5561. Y

currentrvariati'ons 11 at common junction 122'` .of FIG:S=4', forexample. fThe'poin'ts oflonnectionand ,there'sistor v `values'ofthemasle are selectediso'tlratthe peak 2Min; v `"w'a'vefcnrm 204 occurs attheltimeithat a signal represent# -ying -a 'normallypositioned characterVis centered in the register.Y V--As'zshovvn above,V this should occuryon the 80th. I

` shift pulseyforthe:example.shown'in,FIGURS 6-8`- fBrolrenjliriei'206;represents -the threshold Ilei/e1,offtlne 'circuit to l.which thejconrrnon junctionj -is connected; l in 'this example transistor 148;'.CharactersV linthe 'group to:

iIf theoututof fnnask'jllt isbelow level-206th" `determined level,V forone or more of the characters rre'` jectevd bypthefirstvmask.; Similarlythe third maskmay recognize one or lmore of the charactersrecognized-'by nized lbygthevsecond mask. The .only `limitation :placedon ktaneo'usly by all three masks'. I

.. Turningroncefagain'to the example of FGSL SA-SC Y the`maslgrepresented'by FIG, 57A.v will providean output "signal whichexceedsvfthe V.rcrnitputrlevrel if thedetter zV is` Y scanned and mayalso provide an output. signal exceeding theffthreshold level in,response to Aonez-or more=ofthe any other small lower casevletter. The.maskrepresented oy FIG. 5B {will Inot'produce an oiitputsignval`exceeding.

the' selected threshold {levelforthe letters-1a, c, 'eg ynlY o;

1;, u, v, wv andx but `will produce an outputsig'nal exceed?.fing*the*:thresholdilevelin vresponse to the scanning of Vz and possiblysand m; I-Ioiifeveronly they letter `z will cause `botho'fthemaskstoexceed vthefthreshold level.`v

in the tablesvof'FIGS. 5A vand` 5l3 thefpositive numerals indicatefaresistor. connected lto the1blaclcf 'outf put of` thatv stage; while thenegative numerals lindicate a 's Y 'resistorv connected pto. the whiteoutput off-thatstage.VV rvrIlle. magnitude' ofV each. numeral 'isz'proportional tothe. magnitude of the-'current tofbefsuppliedbythat-stage to Ithe common junction Vand, is approximatelylinverselyproptartionalfmv rthe' Yresistance of *the resistor' connected to f'that-stage;l It-hasf beenfound in practicethat itis not f necessarygto`maintain the exact.currentratiosgiven in* FIGSE-v jAfand .513.vv FIG.`5 C`is a .-tablel-v-slhowtng lthe standard. commercial-resistor valuesinthou anfdfsfof ohms t j-which *gu/illV approximate they current'ratio'sindic-ated in emitter of transistorvlSZ, and hence thetemitter.of trani sistorf154,. willbeheld 'at aipotential which isless than if(f A Y the;` potential ofthe basfezof transistor '154.1 VThus ltran-JTysister 154 Willbe heldvoff and transistor 155: will bev heldv nong-Ifz',thesfontput of thev mask exceeds level 2tl6,.thef

strobe pulse .on input 156 is j permitted to raise .the emitter?? if voftransistor ,ltto the rpoint `where@v this;transistor;con. f lductsandtransistof-y .15S isturnedoff.-- Transistor T154@.'vvill'tcontinuef to conductfuntilptlie potentialkofkk input lead,lfallsf .teja potential below. that of the base', 'oftran- .Y sista-54.1 1 1 t j f y Iftransis'torl 155 and/or either'l'one'fof itsco'unte'ryparts 'in `circuits Mifand-` 155beis conductingoutpLtfl()uivvilly vbe held at', groundfpotential by conductionthroughdiode l 158.` However ifthethresliold .is exceeded?in'allthree Y-`j'circuits .148,1W l`49.,and. 15() 'therewill beriofconducting5y ltransistor.connecte-fd to-diod'e'l'SS; hence .output terminal-.rVV

Vvlltl willfbe permitted' totjvgo negative and. thus-generatef.recognition signahv fw f f ofgach mask are so selected that Veachfmasli`vvill provide L .thatpartul-arfmaski Since 1"each masklrtperfor' of.Athergroup toV yfb the necessary comparison between Ythearesponse of `the1 `mas'lrfto variouslscannedifcharactersand,toevaluate the effectikofuchanging one or more2pararneters:ofk a'give'n-ji n vmarslf..y Ingeneralv it Will be found tha-fthev improved mask f y y: will' reject:Vboth the L selected :small VIgroup ofszcliaracters' f v employed inLtheftentative l.design and'gother:characters asvvfwellgj .A masle'forthesecondpathim'ay then-be selected f t similar ,1 fashionwhich willArecognize[thefselectedf charactet'f--andrejectfa Aselectedgroup'ofiithev characters lrecognized,'by the-firstlmasktlf2'rnoretharr--onefcharA aoter' is` recognized..both? bythe lrirst. maslcfand"byVV .theV` j secondrnasls,u "a'tthird mask may;ybe;y selectedV yvhich'jwill differentiate Vabete/Keen the `charactersvto-fbe l recognized andn i.

the restricted jgroup offcharac'teiis recognized bythe other i fmemasks)1 i f 1 'f f Y l Y sfthe sam typefof function YS'aSallotherfiriasksLthedesignt considerations.,forcone v v '1jmaskare'thefsame asy for;all` masks`.z. Therfinal'selection of theypointsV Lof connection-and ;.resistance. values for i each'masleis;best determined empiricallygby trial and Y error.y The :final selectionof the parameter'ssofthemask n canfrbe" expedited t if a tentative 1mask' "s 'fselected 'Whichf i ,rtactersgf YThe tentative irnaslgmayftheanderrorfto maximizethe differences t a given ,character andtheselectedinterferencel'characters.Y

.lt`l1e` iimprovedmask`istheir comparedyvith-all` characteS.. i

' e Scanned. fAny largefscale Vgeneral purpose .digital imputer canbe"prograrnrnechtofniake terfering char; -f alterediby trialV".riossaanaarg The minnaar'zeremeros;Sanna` 1 'Y SB'pindicat zthatnoconnefctijon'isfrnad tothatstagejforv It lies within the in the artWithin the scope of the invention. Acco-rds ingly we desire .the scopeof the inventionl to be limited vonly by the appended claimss.v

We claim: l. In a characterirecognition system which includes means forscanning an area which includes a character yto be recognized, saidscanning means including means for generating time spaced-signalsrepresentative of the character scanned, a multi-stage shift register,means for setting said shift resister to represent said time' spacedsignals, means for repeatedly shifting stage by stage the signals storedin said shift register, a plurality of individual characterrecognition-circuits each arranged to providel an output signal inresponse to the scanning `of a different vselected character, at leastone of said in-v ,K dividual character recognition circuits comprising aplurality of resistor-correlation masks, each of saidresistorcorrelation masks comprising a plurality of resistors, oneter-minal of each of said resistors of a mask being connected to acommon voutput terminalfof that mask, a second terminal of each of saidresistors of a mask being connected to an-output of a respective oneof'said stages of said shift register, a coincidence circuit having aplul@ Y acters being diierent for earch mask, only one character beingcommon to all said groups of characters, and wherein said coincidencecircuit provides a selected outpu-t siglevels scanning of correspondingcharacters which said system is capa-ble of recognizing, said systemcomprising means forscanningY an area which includes a character to berecognized,said scanning means including means for generating timespaced signals representative of the character scanned, a-plurality ofindividual character recognition circuits each provided With one of saidoutput connections and each arranged to recognize a different character,at least one of said individual character recognition circuitscomprising a plurality of resistorcorrelation masks and a coincidencecircuit, each of said resistor-correlation masks `comprising a pluralityof resistors having first and second terminals, the rst terminal of eachof said resistors of a mask being connected to a common output terminalof said mask, said coincil dence circuit having a plurality of inputs,means conrality of inputs, and meansconnecting each input of saidcoincidence circuit to a corresponding one of said com- Y mon terminals.

2.k A system in accordance with claim 1wherein the values of VsaidAresistors and the stages to which said resistors are connected are suchthat the signal presentV at each common terminal of saidmask has anamplitude level 'above apreselectedlevel forf'thatA mask only inresponse to settings of said shift register which are representative ofa selectedgroup of characters, said group Y characterbeing common to allsaid groups of characters.

3.`Inl a character recognition system vwhich includesl means forscanning an area whichincludes a character to; be recognized, saidscanning means including means v Vforfgenerating time spaced signalsrepresentative of the character scanned, 'a multi-stage shift register,eachv stage of said shift-register being adapted to be set Ito registercharacter information, each stage of the shift register having first andsecond complementary outputs, means for setting said shift register torepresent said time spaced I signals, and means for repeatedly shiftingstage by stage the signals stored in said shift registena plurality ofindividual character recognition circuitsre'ach arranged to provide anoutput signal in response to the scanning of a diierent selectedcharacter, at least oneoi:` said individual character recognitioncircuits comprising, a pluy rality of resistor-correlation masks,-eachof said resistorcorrelation masks comprising a plurality of resistors,.one terminal of each of said-resistors of a mask being connected to acommon output -terminal of said mask, a second terminal of each of saidresistors of .a mask being connected to one of saidcomplementary-outputs of a respective one of said stages of said shiftregister, a coincidence circuit having a plurality ofinputs, and meansof characters being differentfor each mask, only one 'I connecting eachinput ofy said coincidence circuitv -to a correspondingone of said'common terminals.

4. A system in accordance withclaim 3@ wherein the values of saidresistors yand the stages to which said renecting each input of saidcoincidence circuit to a corresponding one of said'common terminals, andmeans coupling .the-output of said coincidence circuit to said outputconnection of said one character recognition circuit, and coupling meanscoupling said individual character recognition circuits to said scanningmeans, said coupling means including means -for supplying signalsrepresentative of selected ones of said time spaced signals to saidsecond terminals of said resistors of said masks, said last-named Vmeansincluding means forrepeatedly changing the selected time spacedsignalsfrepresented at said second terminals ofsaid masks, each of saidVmasks of an individual characterrecognition circuit having a differentresponse to the changing, time spaced signals supplied thereto. Y

6. A character recognition system for providing signals at respectiveoutput connections in response to thev scanning of correspondingcharacters which saidgsystem isy capable of recognizing, said system'lcomprising means kfor 'scanning an area which includesV a character tobe recognized, said scanning means including means for generating timedIspaced signals representative of the character scanned, a plurality ofcharacter recognition circuits each provided with one of said outputconnectionsA and each arranged to recognize a different character', at

least one of said character recognition circuits comprissing a pluralityof resistor-correlation masks'and a coincidence circuit, each of saidresistor-correlation masks comprising a plurality of differently-valuedresistors eachl v having rst and second terminals, the irst terminals ofeach of said resistors' of -a mask being connected to a common outputterminal of said mask, said coincidence circuit having'a plurality ofinputs, and means connectingeach of said inputsof vsaid coincidencelcircuit to a corresponding one o f saidcommon terminals, the out-Aputtermi'nal of said coincidence circuit comprising said outputterminal of the character recognition circuit in which it is included,and coupling means for coupling Y said scanning means to the yinputs ofsaid character recognition circuits, said coupling means including meansfor supplying signals representative of selected ones of said Vtimespaced-signals to said second terminals of saidV m time intervals each,where m and n are integers greater than one, means associated with saidscanning means for generating a signal having a rst value for timeinterrrW Yvals'in Whichsaid scan coincides with a character part and asecond'value for time intervals in whichsaid scan 1' does notcoincide-With a characterp-art, a plurality of individual characterrecognition circuits eachjarranged K to recognize a differentcharacter,; at least oneiof .said

plurality of 4resistor-'correiation masksand a coincidence circuit, eachYof said resistor-correlation masks comprising a plurality yofdifferential valued resistors, each re-l sistorhaving a firstterminaland a second terminaL'the 4individual character"recognitionvcircuits comprising a j first terminal of yeach of` s aid resistorsof amask being v, connected to a common output terminal' ofV said mask, l

y' said coincidence circuit havingk a plurality of inputs, and

means connecting each inputoffsaidcoincidence circuit toa correspondingone of saidrcommon terminals; and coupling means coupling said scanningYmeans and said f individual character recognition circuitsrsoiastot'supply signals representative offisignals? generated` in lselectedYtime `intervals to saidy second yterminals'cof ;said"resstor`s lineach'of s'aid masks, aditerenhgroup ofv time intervals being representedatcachoty saidfmasks, Vsaid'c'oupling means including mean-s` forrepeatedly. changing `the time intervals represented ineeach of saidgroups.

' References Citedxin the le of' this patent j "UNITED'STATES' PATENTS,

1. IN A CHARACTER RECOGNITION SYSTEM WHICH INCLUDES MEANS FOR SCANNING AN AREA WHICH INCLUDES A CHARACTER TO BE RECOGNIZED, SAID SCANNING MEANS INCLUDING MEANS FOR GENERATING TIME SPACED SIGNALS REPRESENTATIVE OF THE CHARACTER SCANNED, A MULTI-STAGE SHIFT REGISTER, MEANS FOR SETTING SAID SHIFT RESISTER TO REPRESENT SAID TIME SPACED SIGNALS, MEANS FOR REPEATEDLY SHIFTING STAGE BY STAGE THE SIGNALS STORED IN SAID SHIFT REGISTER, A PLURALITY OF INDIVIDUAL CHARACTER RECOGNITION CIRCUITS EACH ARRANGED TO PROVIDE AN OUTPUT SIGNAL IN RESPONSE TO THE SCANNING OF A DIFFERENT SELECTED CHARACTER, AT LEAST ONE OF SAID INDIVIDUAL CHARACTER RECOGNITION CIRCUITS COMPRISING A PLURALITY OF RESISTOR-CORRELATION MASKS, EACH OF SAID RESISTORCORRELATION MASKS COMPRISING A PLURALITY OF RESISTORS, ONE TERMINAL OF EACH OF SAID RESISTORS OF A MASK BEING 